The mechanical, optical, and electrical properties of materials depend in large part on the crystallized structure of the material. Therefore, the ability to manipulate and control the crystal structure of materials has wide applications. One of these applications is the fabrication of organic semiconductors.
In contrast with typical inorganic semiconductor fabrication techniques, organic semiconductors are constructed via deposition of amorphous thin-film materials. Fabrication techniques may include soluble, conjugated polymers prepared via solution processing methods or—if insoluble—then deposited via vacuum sublimation. Common examples of solvent-based coating techniques include drop casting, spin-coating, doctor-blading, inkjet printing and screen printing. Vacuum based thermal deposition of small molecules requires evaporation of molecules from a hot source. The molecules are then transported through vacuum onto a substrate. Condensation of these molecules on the substrate surface results in thin film formation. Regardless of technique, the organic material deposited onto the silicon substrate is typically referred to as a thin-film layer. Subsequent processing of the thin-film layer may include an annealing step in order to promote crystal growth in the thin-film layer, thereby increasing the carrier mobility of the device.
In particular, carrier mobility is one of the most important factors in determining the performance of organic devices. However, current fabrication techniques oftentimes provide wide ranges of carrier mobilities. It would be desirable to develop fabrication techniques that not only would increase carrier mobility of organic semiconductor devices but that also would improve the predictability of organic semiconductor devices.
A number of other applications may benefit from the ability to control the patterning and crystallization of materials deposited in a disordered state, whether those materials are deposited as thin-film materials or larger, three-dimensional materials.